Field of the Invention
The invention relates generally to GNSS systems, and in particular, to GNSS systems that perform jammer detection.
Background Information
Global navigation satellite systems (GNSS) provide ranging signals that are utilized in applications that determine global positions for surveys, global positions for delivery trucks, global positions for aircraft at and/or approaching airports, and so forth. As is well known, GNSS antennas receive signals from a plurality of GNSS satellites and associated GNSS receivers determine positions based on the timing of codes and carriers in the received GNSS satellite signals.
Increasingly, jamming devices are utilized to transmit jamming signals to intentionally disrupt position calculation operations performed by particular GNSS receivers. A portable jammer may be used, for example, on a delivery truck, to transmit jamming signals to the GNSS antenna located on the truck, in order to occasionally disrupt operations that track the movement of the truck. The jamming signals may also unintentionally disrupt the operations of other GNSS receivers in the same area. For example, the truck may be on a highway traveling by an airport and may disrupt the operation of GNSS receivers at and/or near the airport that are utilized to determine global positions of the aircraft.
The jamming signals have the same or near the same frequencies as the GNSS satellite signals. Further, the received jamming signals have a much higher power than the received GNSS satellite signals because the distance between the jamming device and the GNSS antenna is much shorter than the distance between the GNSS satellites and the GNSS antenna. Thus, the jamming signals overwhelm the GNSS satellite signals at the GNSS receivers, such that the GNSS receivers may not be able to track the codes in the received GNSS satellite signals.
Currently, GNSS jammer detectors determine position and velocity information associated with a jammer based on the detected direction of the received jamming signals, typically with an accuracy of approximately 5 m at a 200 m distance. While the jammer detector systems provides useful information as to the general location of and/or route traveled by the jammer, it does not provide sufficient information to readily identify the jammer.